Exploring data: graphs and numerical summaries
5.8 Sample variance
It is worth noting that a special term is reserved for the square of the sample standard deviation: it is known as the sample variance.
The sample variance
The sample variance of a data sample x 1, x 2, …, xn is given by
where 
is the sample mean.
Example 3: Calculating the variance
The variance of the eleven β endorphin concentration differences is
OpenLearn - Exploring data: graphs and numerical summaries
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